Primary exercises
- Manually created factor.
In a study participants were asked whether their sport activity is
none, oncePerWeek, severalPerWeek
or daily.
Build a proper factor for the responses below and store it in a variable
w.
Print the factor.
Write the code to count the numbers of occurrences of each level and
print the counts.
severalPerWeek, none, none, oncePerWeek, oncePerWeek, oncePerWeek, oncePerWeek, ?, none, none
v <- c( "severalPerWeek", "none", "none", "oncePerWeek", "oncePerWeek", "oncePerWeek", "oncePerWeek", NA, "none", "none" )
w <- factor( v, levels = c( "none", "oncePerWeek", "severalPerWeek", "daily" ) )
w
[1] severalPerWeek none none oncePerWeek oncePerWeek oncePerWeek
[7] oncePerWeek <NA> none none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 5 × 2
f n
<fct> <int>
1 none 4
2 oncePerWeek 4
3 severalPerWeek 1
4 daily 0
5 <NA> 1
- A factor with a random content.
Read help about the function sample.
Then study and try the following lines of code to understand the
results.
Next, understand why an error is generated and use replace
argument to generate a vector with 100 samples.
Store this vector in a variable v and build a factor
w from it.
Finally, count the numbers of occurrences of each level in
w.
Ensure, that levels are in order provided in the variable
lvl.
lvs <- c( "none", "oncePerWeek", "severalPerWeek", "daily" )
sample( lvs, 3 )
[1] "oncePerWeek" "daily" "none"
sample( lvs, 3 )
[1] "daily" "none" "oncePerWeek"
sample( lvs, 3 )
[1] "none" "severalPerWeek" "daily"
sample( lvs, 100 )
Error in sample.int(length(x), size, replace, prob): cannot take a sample larger than the population when 'replace = FALSE'
v <- sample( lvs, 100, replace = TRUE )
w <- factor( v, levels = lvs )
w
[1] daily severalPerWeek daily oncePerWeek none daily
[7] severalPerWeek oncePerWeek daily oncePerWeek daily none
[13] severalPerWeek oncePerWeek none none daily oncePerWeek
[19] oncePerWeek daily daily daily oncePerWeek oncePerWeek
[25] oncePerWeek daily daily severalPerWeek oncePerWeek none
[31] oncePerWeek severalPerWeek none severalPerWeek daily oncePerWeek
[37] oncePerWeek none severalPerWeek daily daily daily
[43] daily daily none oncePerWeek daily none
[49] daily oncePerWeek none none daily oncePerWeek
[55] daily severalPerWeek none none daily severalPerWeek
[61] none oncePerWeek daily none oncePerWeek severalPerWeek
[67] daily severalPerWeek daily severalPerWeek severalPerWeek daily
[73] none oncePerWeek none severalPerWeek daily none
[79] none none daily daily severalPerWeek none
[85] oncePerWeek none daily daily severalPerWeek severalPerWeek
[91] oncePerWeek none severalPerWeek severalPerWeek severalPerWeek severalPerWeek
[97] none daily none severalPerWeek
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 4 × 2
f n
<fct> <int>
1 none 25
2 oncePerWeek 21
3 severalPerWeek 22
4 daily 32
- Reordering factor levels.
When a factor is shown on an axis of a plot, the order is given by its
levels.
The factor w from the previous exercise will be then shown
in this order: none, oncePerWeek,
severalPerWeek, daily.
But for a picture in a manuscript the following order might be needed:
daily, severalPerWeek,
oncePerWeek, none.
Apply to w one of the fct_ functions from the
tidyverse library to produce a factor w2 with
the requested order.
Show the levels of w2.
Again show the number of elements of each level in w2 and
compare it with the table of the previous exercise.
w2 <- fct_relevel( w, c( "daily", "severalPerWeek", "oncePerWeek", "none" ) )
levels( w2 )
[1] "daily" "severalPerWeek" "oncePerWeek" "none"
fct_count( w2 )
# A tibble: 4 × 2
f n
<fct> <int>
1 daily 32
2 severalPerWeek 22
3 oncePerWeek 21
4 none 25